Tubular anchor

ABSTRACT

A tubular anchor to be inserted into a bore formed in a constructional structure and including a hollow anchor body ( 1 ), and a trapezoidal thread-shaped profile ( 2 ) provided on at least a portion of an outer surface of the anchor body ( 1 ) and having a crest region ( 3 ) and a root region ( 4 ) both extending parallel to a longitudinal axis of the anchor body ( 1 ), with the at least flanks of a trapezoidal cross-section of the profile ( 2 ) remote from an end of the anchor body ( 1 ) facing in a setting direction being inclined with respect to the longitudinal axis of the anchor body ( 1 ) at an angle (α) from 10° to 45°.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a tubular anchor, in particular, for mine and tunnel construction for insertion in a bore formed in a mine or tunnel gallery, with the tubular anchor having a hollow anchor body, and a trapezoidal thread-shaped profile provided on at least a portion of an outer surface of the anchor body and having a crest region and a root region both extending parallel to a longitudinal axis of the anchor body.

[0003] 2. Description of the Prior Art

[0004] Tubular anchors are generally known. They function primarily as roof bolts for stabilization of walls of hollow spaces such tunnels, galleries and the like. They are used primarily for securing to each other following each other, in a direction transverse to the wall, the wall-forming strata. In many cases, the mechanical characteristics of the layers, which lie in immediate vicinity of the wall surface, in particular, their supporting resistance, changes as a result of formation of a hollow space. Therefore, these layers need be secured to further located, undamaged or unaffected layers or strata. The tubular anchor is primarily secured in a bore with a mortar mass. As a mortar mass, e.g., a two-component adhesive, in particular, an epoxyacrylate resin with a hardener, is used. The mortar mass is intermixed and hardens, anchoring the tubular anchor in the bore. The end of an anchor rod, which projects from the bore, is, in most cases, provided with a thread. A constructional component is secured on the projected end of the anchor rod with a nut.

[0005] A tubular anchor of the type discussed above is disclosed, e.g., in German Utility model DE 29 501 638. The known tubular anchor is formed of an anchor body provided with a shaped profile. The shaped profile is formed as a single trapezoidal thread. This insures the possibility to use the tubular anchor with a conventional drilling tool.

[0006] The drawback of the known tubular anchor consists in that the holding value of the known anchor is substantially reduced in case fissures or cracks are present in the bore region.

[0007] Accordingly, an object of the present invention is to provide a tubular anchor with such a profile that would insure a high holding value even in a cracked constructional component.

[0008] Another object of the present invention is to provide a tubular anchor that can be easily and rapidly set in a bore.

SUMMARY OF THE INVENTION

[0009] These and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a tubular anchor with trapezoidal thread-shaped profile in which at least the flanks of a trapezoidal cross-section of the profile remote from an end of the anchor body facing in a setting direction are inclined with respect to the longitudinal axis of the anchor body at an angle from 10° to 45°.

[0010] The foregoing profile of the thread insures a secondary expansion of the inventive tubular anchor. The secondary expansion takes place, in particular, when the tubular anchor is provided with an anti-stick coating or the mortar mass is so formed that no adhesion occurs between the mortar mass and the anchor. Further, the foregoing inclination of the profile flanks favorably influences the setting process. The inclination of the flanks, together with high cohesion of the mortar mass insures retention of the inventive tubular anchor in a bore of a constructional component during the setting process. Thereby, the holding time, during which the tubular anchor should be stably held in the bore until the mortar mass becomes almost completely hardened, is eliminated. An optimal secondary expansion is obtained when the flanks are inclined at an angle of about 20°. To insure a simple formation of the trapezoidal thread, advantageously, both opposite flanks have the same inclination.

[0011] In order to insure a sufficiently high holding value, the axial extent of the root region is so selected that it corresponds to from 0.04 to 0.1 times of the diameter of the anchor body. With the tubular anchor being set, the mortar mass fills the space between the flanks. Upon application to the anchor of a load, which acts in a direction opposite to the setting direction, shear forces act on the mortar mass. Therefore, the cross-section of the mortar mass, which fills the space between the flanks, plays a decisive role in insuring a lasting connection between the tubular anchor and the mortar mass. This cross-section is determined to a significant extent by the axial extent of the root region, which axial extent is determined by the diameter of the anchor body. The diameter of the anchor body, in turn, depends on the applied maximal load.

[0012] The axial extent of the crest region is also so selected that it corresponds to from 0.04 to 0.1 times of the anchor body diameter. Thereby, the profile of the anchor can withstand sufficiently high shear forces generated by the load resulting from tightening of the nut or the like.

[0013] The height of the profile in the radial direction, advantageously, corresponds to from 0.25 to 0.75 times of the wall thickness of the anchor. This insures an economical manufacturing of the profiled tubular anchor.

[0014] The threaded profile has, preferably, a pitch from 10 mm to 40 mm. This insures a uniform distribution of the mortar mass between the bore wall and the profile of the tubular anchor. In addition, the profile formed according to the present invention, increases the holding value, with which the inventive tubular anchor is held in the constructional component, insuring, at the same time, an adequate removing rate with which the drilling dust is removed. Optimally, the thread pitch should be about 15 mm.

[0015] Advantageously, the profile thread is formed as a double thread. This further increases the removing rate, with which the drilling dust is removed, which rate is substantially higher than with a single thread profile. Furthermore, the undercut surface, which the mortar mass engages, also increases twofold in comparison with a single thread profile. When the inventive tubular anchor has to meet particularly stringent requirements, a triple or multiple thread profile can be used.

[0016] Advantageously, the profile extends over the entire length of the anchor body. In this case, the thread profile serves as holding means for a mortar mass and as load application means for, e.g., a nut. This permits to avoid the use of a separate thread for forming the load application means.

[0017] The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to is construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Single FIGURE of the drawings shows a longitudinal, partially cross-sectional view of a tubular anchor according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] A tubular anchor according to the present invention, which is shown in the drawing, has a hollow tubular anchor body 1 provided on its outer surface, at least partially, with a thread-like profile 2. The thread-like profile 2 is formed as a trapezoidal thread with a crest region 3 and a root region 4 extending both parallel to the longitudinal axis of the anchor body 1. Each root region 4 is connected with two adjacent crest regions 3 by respective flanks. The length of each of the crest region 3 and the root region 4, which is measured in the axial direction, corresponds approximately to 0.04-0.1 of the diameter d of the anchor body. The inclination angle α of each flank with respect to the axial direction amounts approximately to 10°-45°.

[0020] The thread is formed as a double thread with a pitch of about 15 mm. The thread extends over the entire length of the anchor body 1 and functions as retaining means for a mortar mass, on one hand, and as load application means for, e.g., a nut, on the other hand. The height h of the thread measured in a direction transverse to the axial direction corresponds approximately to 0.25-0.75 of the thickness of the anchor body wall.

[0021] Though the present invention was shown and described with references to the preferred embodiments, such are merely illustrative of the present invention and are not to be construed as a limitation thereof, and various modifications of the present invention will be apparent to those skilled in the art. It is, therefore, not intended that the present invention be limited to the disclosed embodiments or details thereof, and the present invention includes all variations and/or alternative embodiments within the spirit and scope of the present invention as defined by the appended claims. 

What is claimed is:
 1. A tubular anchor to be inserted into a bore formed in a constructional structure, comprising a hollow anchor body (1); and a trapezoidal thread-shaped profile (2) provided on at least a portion of an outer surface of the anchor body (1) and having a crest region (3) and a root region (4) both extending parallel to a longitudinal axis of the anchor body (1), wherein at least flanks of a trapezoidal cross-section of the profile (2) remote from an end of the anchor body (1) facing in a setting direction are inclined with respect to the longitudinal axis of the anchor body (1) at an angle (α) from 10° to 45°.
 2. A tubular anchor according to claim 1, wherein an axial extent (a) of the root region (4) corresponds to from 0.04 to 0.1 times of a diameter (d) of the anchor body (1).
 3. A tubular anchor according to claim 1, wherein an axial extent of the crest region (3) corresponds to from 0.04 to 0.1 times of a diameter (d) of the anchor body (1).
 4. A tubular anchor according to claim 1, wherein an axial extent (b) of the crest region (3) corresponds to an axial extent (a) of the root region (4).
 5. A tubular anchor according to claim 1, wherein an the profile (2) has, in a direction transverse to the longitudinal axis of the anchor body (1), a height (h) corresponding to from 0.25 to 0.75 times of a wall thickness of the anchor body (1).
 6. A tubular anchor according to claim 1, wherein the trapezoidal thread-shaped profile (2) has a pitch from 10 mm to 40 mm.
 7. A tubular anchor according to claim 1, wherein profile-forming trapezoidal thread is a double thread.
 8. A tubular anchor according to claim 1, wherein the trapezoidal thread-shaped profile (2) extends over an entire length of the anchor body (1).
 9. A tubular anchor according to claim 1, wherein the trapezoidal thread-shaped profile (2) has an anti-stick coating (5) for preventing adhesion of a mortar mass to the profile (2). 